Wednesday, April 29, 2009

Emory University environmental studies professor Uriel Kitron was in Australia last week, assisting health authorities in an outbreak of dengue fever in the state of Queensland, when news broke about the swine flu epidemic in Mexico.

Global travel and human alterations to the environment, such as rapid urbanization, are helping to fuel some infectious diseases outbreaks, says Kitron, also chair of the environmental studies department at Emory and an internationally known researcher of the eco-epidemiology of infectious diseases. Kitron's research focuses on vector-borne diseases carried by insects and ticks and the zoonoses – diseases shared by humans and animals.

"In many developing countries, people are moving from rural areas to mega-cities, where they continue to practice subsistence agriculture," Kitron says. "Whenever you have large concentrations of people, domestic animals and poor sanitation and water supply, you have many opportunities for disease transmission."

Deforestation and other human changes to the landscape are other drivers of emerging infectious diseases, he added. "For example, when you bring agriculture into formerly forested areas, you change the migration patterns of animals and expose people and their livestock to more contact with wildlife," he explains.

Stemming Dengue Fever in Australia

Unusually hot, wet weather, a rapidly developing strain of the dengue virus, and a human traveler created "a perfect storm" for dengue fever in Queensland, Australia – which is experiencing its worst outbreak in two decades. About 1,000 people have become ill with the mosquito-borne illness. Dengue fever causes severe headaches and joint pain, and exposure to a second strain can result in hemorrhagic fever and death.

Kitron joined other experts in assisting Queensland health authorities. Kitron specializes in spatial epidemiology – using geographic information systems (GIS) and other methods to gather environmental data and create maps to pinpoint disease agents and their vectors in time and space.

The outbreak was traced to a patient who had recently traveled to Papua, New Guinea. "Although quite sick, he didn't go to a doctor for several weeks," Kitron says. "Whenever you have a lag time in diagnosis like that, you miss opportunities to prevent the spread of an outbreak."

Queensland's public health efforts – combined with cooler, drier weather – appeared to have stemmed the dengue fever outbreak for now. However, Kitron says the virus may be re-introduced, or could over-winter and re-emerge in the next hot season.

The Queensland government is now considering investing in spatial analysis software. Kitron plans to return for a workshop on using the technology to aid in the response for future outbreaks.

"Use of GIS and spatial statistics can help health authorities determine which cases are more likely to lead to other cases, so that they can better target which houses should be sprayed for mosquitoes immediately, and which ones can wait," Kitron explains.